Regenerator matrix

ABSTRACT

A matrix disk for a rotary regenerator is made up of spiral turns of a first strip having spaced apart corrugations all orientated in the same direction inclined at an angle to the face of the disk and a second strip having spaced apart corrugations all orientated in the same direction inclined at an angle to the face of the disk in the opposite direction from that of the corrugations of the first strip.

Umted States Patent 1191 1111 3,910,344

Hagen 1 Oct. 7, 1975 [54] GENERATOR MATRIX FOREIGN PATENTS OR APPLICATIONS lnventorl Robert Hagen, P L 1,451,156 2/1969 Germany 165/10 [73] Assignee: General Motors Corporation,

Detroit, Mich. Primary Examiner-Albert W. Davis, Jr. Filed: Mar. 1.974 Attorney, Agent, or Firm-Arthur N. KreIn [21] Appl. No.: 455,047 [57] ABSTRACT A matrix disk for a rotary regenerator is made up of 52 U.S. c1. 165/10 Spiral mm of a first strip having Spaced apart Comb [51] Int. Cl F28d 19/00 gations a orientated in the Same direction inclined at Fleld of Search 165/10, 4 an angle to the face of the disk and a Second Strip ing spaced apart corrugations all orientated in the [56] References C'ted same direction inclined at an angle to the face of the UNITED STATES PATENTS disk in the opposite direction from that of the corruga- 1,808,921 6/1931 Frankl 165/10 tions of the first strip. 3,183,963 5/1965 Mondt 165/10 3,252,506 5/1966 Huebner, Jr. 165/10 3 Clalms, 6 Drawmg Flgul'es REGENERATOR MATRIX This invention relates to a matrix disk for a rotary regenerator heat exchange apparatus and, in particular, to a regenerator matrix of the axial-flow or disk type. Rotary regenerators, particularly of the axial-flow type, utilize heat transfer means in the form of a porous 1 metal or ceramic disk matrix which is rotated so that each element thereof passes successively through two aeriform fluid flow paths, absorbing heat from a hotter fluid and releasing it to a cooler fluid in these flow paths.

Metal matrices ordinarily are made up of a crimped or corrugated metal sheets spirally wound into a disk and then brazed or otherwise bonded together so as to provide a rigid cellular or porous structure. In regenerators of the sort to which this invention is particularly applicable, the major portion of the disk is heated to relatively high temperatures of the order of up to l450F. or higher, whereas the rim or radially outermost portion of the disk is contacted around the perimeter by the relatively cool air and thus is at substantially lower temDerature. Other factors may cause temperature gradients but, in general, whatever the reasons for the difference in temperature between different radial zones of the matrix, the result is differential expansion with attendant overstressing and yielding of the parts and resulting cracking. Thus, substantial separation in a generally radial plane has been observed in operation of metallic rotary regenerator matrices.

Conventional structure of such an axial-flow regenerator matrix involves alternating flat and corrugated strips or alternating corrugated strips which are spirally wound to form the matrix. One example of such flat strip and corrugated strip structure is illustrated in U.S. Pat. No. 3,276,5 for Gas Turbine Regenerator issued Oct. 4, 1966 to James H. Whitfield. In a structure of this sort, the matrix is quite rigid once the strips are brazed together. Although the corrugated strip can give, the flat strip between the layers of corrugated strip is substantially unyielding. Thus, when the interior of the matrix becomes hotter than the outer zone, high hoop stresses are set up in the flat strips of the outer part of the matrix.

An example of alternating corrugated strips structure is illustrated in US Pat. No. 3,532,157 entitled Regenerator Disk issued Oct. 6, 1970 to William S. Hubble wherein a corrugated or weakened sheet layer is substituted for the flat sheet layer in an attempt to correct the problem encountered in the use of the flat sheet layer.

The problem of providing a matrix structure is complicated by two facts: One is that there must be such mating between the adjacent strips wound into the ma trix that flow of gas circumferentially of the matrix is prevented, since such flow would result in leakage from the high pressure to the lower pressure of gases flowing through the regenerator. The other complicating factor is that, since the matrix is wound spirally, each course is of different length than the one before. With a flat strip alternating between the turns of corrugated strip, the increase in circumference of each turn or layer presents no problem. However, if two corrugated strips are employed, there will naturally be more corrugations in each turn than in the one immediately inside it,

so that the corrugations will not match uniformly and the successive layers of the matrix will not stack in a proper spiral path. To put it in different terms, at some points the peaks of the corrugations of the sheets will be aligned to provide a large separation where at its other points the peaks of one sheet will fall into the valleys of the other so that the separation is insufficient and, of course, the winding is not close to a uniform spiral.

It is therefore the primary object of this invention to provide an improved matrix disk for rotary regenerators of a construction whereby to provide rectangular geometry flow passages through the matrix to obtain maximum heat transfer performance using economi cally manufactured matrix elements.

It is another object of this invention to provide in a matrix structure a degree of radial flexibility and circumferential flexibility sufficient to accept thermal gradients and transient temperature conditions with acceptable levels of stress, while providing a means of selecting the degree of radial rigidity in the matrix.

A still further object of this invention is to provide a matrix structure with circumferentially orientated rectangular flow passages thereby reducing stresses in matrix flow passage walls caused by pressure differentials between flow passages, as well as by seal contact loads.

These and other objects of the invention are attained by means of a matrix structure in which the heat exchange portion of the matrix isfabricated by the use of a pair of spirally wound corrugated sheet layers, one of the layers having corrugations provided thereon at an angle other than a right angle to the face of the matrix disk while the second sheet layer has corresponding corrugations-but with these corrugations inclined in an opposite direction to the corrugations of the first layer.

For a' better understanding of the invention, as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic view of an axial-flow rotary regenerator taken in a plane containing the axis of rotation of the matrix thereof;

FIG. 2 is an enlarged, end face view of a portion of the heat exchange material of the matrix of FIG. 1 constructed in accordance with the invention with the stack of spirally wound sheets forming the heat exchange material straightened to more clearly show the configuration of these sheets;

FIG. 3 is an end face view of the heat exchange material of the matrix of FIG. 1 showing the spiral winding of the sheet layers thereof; and,

FIGS. 4, 4a and 4b show the various configurations assumed by a corrugation of a sheet layer of the matrix, FIG. 4 showing the corrugation as manufactured, FIG. 4a showing the corrugation under compressive load and FIG. 4b showing the corrugation under tensile load.

Referring now to FIG. 1, there is shown a rotary regenerator heat exchange apparatus which includes a housing 10, generally drum-shaped, to enclose an axialflow matrix 12 which is of such construction so as to define a multiplicity of pores or passages 14, greatly enlarged in FIG. 1, extending from face to face of the matrix generally parallel to the axis of rotation defined by a matrix locating and driving shaft 16. Shaft 16 is suitably journalled in the boss 18 of the housing 10 and terminates in a spider 20 which is coupled to the matrix by means, not illustrated, which may be of the type described in U.S. Pat. No. 3,476,173 entitled Rotary Regenerator Matrix Mount and Drive issued Nov. 4, 1969 to Joseph W. Bracken, .Ir., and William S. Hubble, so that the matrix may be rotated slowly. As is well known, the matrix could alternately be driven through a rim drive, not shown.

The matrix preferably includes a non-porous hub or inner rim 22 and an outer, non-porous, cylindrical rim 24, but such rims are not essential, and a body of heat exchange material 26 made up of metal strips wound to form a disk having parallel faces and pervious to flow generally parallel to the axis of the disk. A generally cylindrical space 28 is defined within the interior of the matrix and a space 30 extends around the periphery of the matrix within the housing 10.

An inlet 32 for cool high pressure air enters one face of the housing and, opposite to it, an outlet 34 is provided for the discharge of compressed air which is heated after having passed through the matrix. I-Iot low pressure exhaust gases enter through an inlet 36 and leave the regenerator through an outlet 38, the two streams being thus in counterflow relation in the embodiment of the regenerator illustrated. As shown, the hot gas passage is of larger area than the cool air passage because of the difference in density between these fluids. Since the exhaust gases entering through the inlet 36 engage first the upper face of the matrix, as seen in FIG. 1, this is the hot side, while the lower face of the matrix is then referred to as the cold side.

A sealing means or seal assembly 40 is provided be tween each face of the matrix and the housing to confine the cold and hot fluids to the desired flow paths through the matrix from inlet to outlet and to minimize leakage between the paths.

The heat exchange body 26 of matrix disk 12 is, in accordance with the invention, made up of alternating corrugated strips 50 and 60 wrapped spirally around the hub 22, this spiral wrapping being shown in FIG. 3, to form, in effect, a spirally wound stack of alternating corrugated strip layers 50 and 60, the corrugations in adjacent layer strips being orientated at different angles. The corrugations on each of the strips extend out from one side only thereof, the opposite side of each strip presenting substantially a flat surface against which the peaks of the corrugations of the adjacent strip abut to define the flow passages 14 through the matrix disk.

As best seen in FIG. 2, the strip 50 is formed with spaced apart, deep, narrow ribs or corrugations 52 with flat sheet or non-corrugated portions 54 therebetween. The corrugations 52 typically are substantially triangular in cross section with an open gap S at the base and each of these corrugations are inclined in the same direction relative to the edges of the strip and thus to the faces of the finished matrix disk. Strip 50, as seen in FIG. 2, can be considered to have left-hand corrugations 52.

Strip 60 is also formed with spaced apart ribs or corrugations 62 with flat or non-corrugated portions 64 therebetween. Corrugations 62 are also typically substantially triangular in cross section with a gap S at the base thereof with each corrugation inclined in the same direction relative to the edges of the strip, but in the opposite direction to those of strip 50, and thus this strip 60 can be considered to have right-hand corrugations, as viewed in FIG. 2. Thus, both the corrugations 52 and 62 of strips 50 and 60, respectively, when viewed from the outside diameter of the matrix, are inclined at an acute angle to the axis of the matrix disk.

The corrugations 52 and 62 of the strips 50 and 60, respectively, may be formed at any desired acute angle relative to the axis of the matrix, but opposite each other, and preferably this angle should be chosen so as not to greatly restrict the flow of the fluid in a direction generally parallel to the axis of the matrix disk. However, the angle should be sufficiently large to ensure that the peak of a corrugation of one sheet cannot enter the valley of a corrugation of the next adjacent sheet in the event that these corrugations are somewhat radially aligned as a result of spiral winding of the strips. Of course, by maintaining the gap S at the base of a corrugation as small as possible, the chance that this will occur is also greatly reduced. Thus, opposite orientation of the corrugations in adjacent strips serves to prevent nesting of the elements which would result if the corrugations in each were parallel, particularly if the gap S is substantial. Maintaining a minimum gap 5 is also desirable as this will produce more perfect rectangular flow passages 14 between adjacent strips.

The angular orientation of the corrugations of the strips 50 and 60 serves to reduce the effective unsupported span of the adjacent strip with which it cooperates, a result which would occur if the corrugations of these strips were parallel to the axis of the matrix. This angular orientation of the corrugations provides a degree of radial rigidity in the resulting structure and will provide support for the previously spiraled sheets during assembly.

The distance for pitch P between corrugations may be selected, as desired, but it should be realized that this pitch distance should be chosen so that when the strips are spirally wound, the sheet does not traverse a full convolution pitch P so that a degree of radial flexibility is maintained. However, it has been found that a measure of radial flexibility can be maintained even if ribs traverse more than a full convolution pitch since alignment of the ribs in subsequent wraps is random.

Ideally, the peaks of the corrugations on one sheet should engage the flat portions of the adjacent sheet, but since these sheets are spirally wound to form the matrix disk, which may be about 2 feet overall in diameter and about 3 inches thick, with the individual sheets forming the heat exchange portion being, for example, of stainless steel, approximately 0.002 inch thick with corrugations in the order of, for example, about 0.13 inch deep, the possibility of a circumferential leak between adjacent flow passages exists. As used herein, the depth of the corrugations refers to the radial dimension of the corrugation relative to the flat portion of the strip from which it extends. Minimizing the gap S at the base of each of the corrugations minimizes the size of potential leakage paths, particularly in a matrix bonded without the aid of a brazing compound. This leak path, however, can be sealed in a matrix bonded using a brazing compound, this being accomplished more readily with corrugations having a minimum gap S.

Some measurable gap S is necessary particularly if a brazing compound is used to bond the spiral wound sheets together to maintain the circumferential flexibility provided by the corrugated sheets 50 and 60, as shown. Bonding without the aid of a brazing compound allows the possibility of near zero gap S. However, some minimum gap S is desired since, as shown in FIGS. 4, 4a and 4b, with a gap S as seen in FIG. 4 for the corrugation as manufactured, this gap as seen in FIG. 4a under compressive load will reduce to a gap size S and, under tensile load, this gap will increase in width to a gap size S" as seen in FIG. 41;. The corrugations of a single formed convolution would vary in configuration from that shown in FIG. 4a to that shown in FIG. 4b during operation of the rotary regenerator. However, where the peak of a corrugation on one sheet crosses the base of a corrugation on the other sheet and is bonded thereto, this particular latter mentioned corrugation may not function in the manner just described, at least at the contact line of the peak across this corrugation.

When the heat transfer portion of the matrix is subjected to radial compressive loads, the flat portions of the respective sheets 50 and 60 will dish or bend somewhat over the peak of the corrugation abutting these normally flat portions. It should also be realized that the portions 54 and 64 of sheets 50 and 60, respectively, referred to herein as flat portions and shown as such in FIG. 2 for purposes of illustration only, would when fabricated into the heat transfer portion of the matrix disk be slightly curved, the radius of curvature depending on the location of these portions radially outward from the hub 22.

Although the sheets 50 and 60 are shown with their corrugations uniformly spaced apart, it is to be realized that, if desired, the spacing of the corrugations could be varied from the inner periphery to the outer periphery of the matrix disk to correspond to the variation in the distance around the matrix from turn to turn because of the spiral winding of the strips 50 and 60. In addition, the depth of the corrugations in the final turn or course of the strips adjacent to the rim 24 can be gradually decreased to maintain a cylindrical outer surface of the heat exchange body adapted to fit into the cylindrical rim 24.

Sheets 50 and 60 may be made of any suitable mate rial such as, for example, a ferritic stainless steel or an austinitic stainless steel, with a material thickness of, for example, 0.001 inch to 0.006 inch thick, typically 0.002 inch thick. The heighth and spacing or pitch P of the ribs or corrugations on these sheets would be preferably 0.012 inch to 0.025 inch, typically 0.018 inch and 0.050 inch to 0.150 inch, typically 0.130 inch, respectively. The rib or corrugation angle is preferably 12 to 4 and typically 1. As will be apparent from the above description of the sheet strips, the drawings showing the subject matrix structure have been exaggerated to more clearly show the details of the matrix structure.

Any suitable method can be used to fabricate the corrugated strips 50 and 60. One suitable method of producing these strips, if made, for example, of stainless steel, is by feeding a flat metal strip to a pair of forming rolls, one of which is equipped with appropriately spaced, radial extending, high strength, forming teeth, while the other roll is of a resilient compound which would conform to the forming teeth of the first roll to thereby produce the desired shape in the strip, the original flat strip from which these strips are to be fabricated being fed into the bite of the forming rolls at a skew angle corresponding to the desired angle of the corrugations relative to the edges of the strip. Alternately, the strips may be fabricated by reciprocating machine forming, not shown, in a conventional manner.

What is claimed is:

l. A rotary regenerator matrix structure of annular form porous to flow of fluid generally parallel to the axis of the matrix and effective to block fluid flow circumferentially around the axis, the matrix structure comprising first and second spiral wound strips with each turn of the first strip disposed between adjacent turns of the second strip and with the strips abutting face to face and fixed together into a rigid, elastic structure, the first strip being provided with spaced apart corrugations inclined at a relatively small angle of approximately /z to 4 in one direction relative to the axis of the matrix, the portion of said first strip between said spaced apart corrugations thereon being substantially flat sheet stock material, the second strip being formed with spaced apart corrugations inclined in the opposite direction and at an equivalent angle to the axis of the matrix from the corrugations of the first strip, the portion of said second strip between said spaced apart corrugations thereon being substantially flat sheet stock material, the corrugations of the first strip and of the second strip having substantial depth radially of the matrix to separate radially the turns of the other strip, the corrugations extending from one side only of each said strip, the opposite side of each said strip presenting substantially a flat surface against which the peaks of said corrugations of the adjacent strip abut to define substantially rectangular fluid flow passages between adjacent strips, the circumferential extent of said passages being defined by said corrugations.

2. A rotary regenerator matrix structure of annular form porous to flow of fluid generally parallel to the axis of the matrix and effective to block fluid flow circumferentially around the axis, the matrix structure comprising first and second spiral wound strips with each turn of the first strip disposed between adjacent turns of the second strip and with the strips abutting face to face and fixed together into a rigid, elastic structure, the first strip being provided with corrugations at spaced apart intervals separated by substantially flat sheet strip portions, said corrugations being inclined in one direction relativeto the axis of the matrix at an angle of approximately Az to 4 to the axis of the matrix, the second strip being formed with corrugations at spaced apart intervals separated by substantially flat sheet strip portions, said corrugations of said second strip being inclined in the opposite direction to the axis of the matrix from the corrugations of the first strip and at the same angle, the corrugations of the first strip and of the second strip having a rib heighth radially of the matrix of from 0.012 inch to 0.025 inch to separate radially the turns of the other strip, the corrugations extending from one side only of each said strip, the opposite side of each said strip presenting substantially a flat surface against which the peaks of said corrugations of the adjacent strip abut to define substantially rectangular fluid flow passages between adjacent strips, the circumferential extent of said passages being defined by said corrugations.

3. A rotary regenerator matrix structure according to claim 2 wherein the spacing of said corrugations on said first strip and said second strip is between 0.050 inch to 0.150 inch. 

1. A rotary regenerator matrix structure of annular form porous to flow of fluid generally parallel to the axis of the matrix and effective to block fluid flow circumferentially around the axis, the matrix structure comprising first and second spiral wound strips with each turn of the first strip disposed between adjacent turns of the second strip and with the strips abutting face to face and fixed together into a rigid, elastic structure, the first strip being provided with spaced apart corrugations inclined at a relatively small angle of approximately 1/2 * to 4* in one direction relative to the axis of the matrix, the portion of said first strip between said spaced apart corrugations thereon being substantially flat sheet stock material, the second strip being formed with spaced apart corrugations inclined in the opposite direction and at an equivalent angle to the axis of the matrix from the corrugations of the first strip, the portion of said second strip between said spaced apart corrugations thereon being substantially flat sheet stock material, the corrugations of the first strip and of the second strip having substantial depth radially of the matrix to separate radially the turns of the other strip, the corrugations extending from one side only of each said strip, the opposite side of each said strip presenting substantially a flat surface against which the peaks of said corrugations of the adjacent strip abut to define substantially rectangular fluid flow passages between adjacent strips, the circumferential extent of said passages being defined by said corrugations.
 2. A rotary regenerator matrix structure of annular form porous to flow of fluid generally parallel to the axis of the matrix and effective to block fluid flow circumferentially around the axis, the matrix structure comprising first and second spiral wound strips with each turn of the first strip disposed between adjacent turns of the second strip and with the strips abutting face to face and fixed together into a rigid, elastic structure, the first strip being provided with corrugations at spaced apart intervals separated by substantially flat sheet strip portions, said corrugations being inclined in one direction relative to the axis of the matrix at an angle of approximately 1/2 * to 4* to the axis of the matrix, the second strip being formed with corrugations at spaced apart intervals separated by substantially flat sheet strip portions, said corrugations of said second strip being inclined in the opposite direction to the axis of the matrix from the corrugations of the first strip and at the same angle, the corrugations of the first strip and of the second strip having a rib heighth radially of the matrix of from 0.012 inch to 0.025 inch to separate radially the turns of the other strip, the corrugations extending from one side only of each said strip, the opposite side of each said strip presenting substantially a flat surface against which the peaks of said corrugations of the adjacent strip abut to define substantially rectangular fluid flow passages between adjacent strips, the circumferential extent of said passages being defined by said corrugations.
 3. A rotary regenerator matrix structure according to claim 2 wherein the spacing of said corrugations on said first strip and said second strip is between 0.050 inch to 0.150 inch. 